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/*
* Copyright (C) 2008 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
var PROGRESS_ELEMENT_ID = "ajax_progress";
var CONNECTION_ERROR_ELEMENT_ID = "ajax_error";
var g_filesLoading = 0;
/**
* Asynchronously get a url that contains a json file, and call the callback
* when done.
*
* The callback should have the following prototype:
* callback(boolean success, Object result)
*
* Returns an object that can be used to cancel the request.
*/
function get_file_contents(url, callback) {
var running = true;
function set_progress_visibility(visible) {
var progress = document.getElementById(PROGRESS_ELEMENT_ID);
if (progress) {
progress.style.display = visible ? "block" : "none";
}
}
show_bad_connection_error(null);
var req;
if (window.XMLHttpRequest) {
req = new XMLHttpRequest();
} else if (window.ActiveXObject) {
req = new ActiveXObject("Microsoft.XMLHTTP");
} else {
return;
}
g_filesLoading++;
if (g_filesLoading > 0) {
set_progress_visibility(true);
}
req.open("GET", url, true);
req.onreadystatechange = function() {
if (req.readyState == 4) {
if (req.status == 200) {
callback(true, req.responseText);
} else {
callback(false, null);
}
g_filesLoading--;
if (g_filesLoading == 0) {
set_progress_visibility(false);
}
running = false;
}
};
req.send(null);
var controller = new Object();
controller.cancel = function() {
req.abort();
if (running) {
g_filesLoading--;
if (g_filesLoading == 0) {
set_progress_visibility(false);
}
running = false;
}
};
return controller;
}
/**
* like get_file_contents, but converts the result to a json object
*/
function get_json(url, callback) {
return get_file_contents(url, function(success, data) {
callback(success, eval("(" + data + ")"));
});
}
function show_bad_connection_error(err) {
var errorDiv = document.getElementById(CONNECTION_ERROR_ELEMENT_ID);
if (errorDiv) {
if (err) {
errorDiv.style.display = "block";
} else {
errorDiv.style.display = "none";
}
}
}
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